- Introduce a new function bremfreel() that does a bremfree with the buf

   queue lock already held.
 - In getblk() and flushbufqueues() use bremfreel() while we still have the
   buf queue lock held to keep the lists consistent.
 - Add LK_NOWAIT to two cases where we're essentially asserting that the bufs
   are not locked while acquiring the locks.  This will make sure that we get
   the appropriate panic() and not another one for sleeping with a lock held.

1 files changed, 14 insertions, 8 deletions

diff --git a/sys/kern/vfs_bio.c b/sys/kern/vfs_bio.c
index 3dbbed6..104043c 100644
--- a/sys/kern/vfs_bio.c
+++ b/sys/kern/vfs_bio.c
@@ -84,6 +84,7 @@ static int vfs_bio_clcheck(struct vnode *vp, int size,
 		daddr_t lblkno, daddr_t blkno);
 static int flushbufqueues(void);
 static void buf_daemon(void);
+void bremfreel(struct buf * bp);
 
 int vmiodirenable = TRUE;
 SYSCTL_INT(_vfs, OID_AUTO, vmiodirenable, CTLFLAG_RW, &vmiodirenable, 0,
@@ -654,12 +655,19 @@ bfreekva(struct buf * bp)
 void
 bremfree(struct buf * bp)
 {
+	mtx_lock(&bqlock);
+	bremfreel(bp);
+	mtx_unlock(&bqlock);
+}
+
+void
+bremfreel(struct buf * bp)
+{
 	int s = splbio();
 	int old_qindex = bp->b_qindex;
 
 	GIANT_REQUIRED;
 
-	mtx_lock(&bqlock);
 	if (bp->b_qindex != QUEUE_NONE) {
 		KASSERT(BUF_REFCNT(bp) == 1, ("bremfree: bp %p not locked",bp));
 		TAILQ_REMOVE(&bufqueues[bp->b_qindex], bp, b_freelist);
@@ -686,7 +694,6 @@ bremfree(struct buf * bp)
 			break;
 		}
 	}
-	mtx_unlock(&bqlock);
 	splx(s);
 }
 
@@ -1865,9 +1872,8 @@ restart:
 
 		if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT) != 0)
 			panic("getnewbuf: locked buf");
-		/* XXX bqlock needs to be held across bremfree() */
+		bremfreel(bp);
 		mtx_unlock(&bqlock);
-		bremfree(bp);
 
 		if (qindex == QUEUE_CLEAN) {
 			if (bp->b_flags & B_VMIO) {
@@ -2141,10 +2147,10 @@ flushbufqueues(void)
 		if ((bp->b_xflags & BX_BKGRDINPROG) != 0)
 			continue;
 		if (bp->b_flags & B_INVAL) {
-			if (BUF_LOCK(bp, LK_EXCLUSIVE) != 0)
+			if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT) != 0)
 				panic("flushbufqueues: locked buf");
+			bremfreel(bp);
 			mtx_unlock(&bqlock);
-			bremfree(bp);
 			brelse(bp);
 			return (1);
 		}
@@ -2176,10 +2182,10 @@ flushbufqueues(void)
 		if ((bp->b_xflags & BX_BKGRDINPROG) != 0)
 			continue;
 		if (bp->b_flags & B_INVAL) {
-			if (BUF_LOCK(bp, LK_EXCLUSIVE) != 0)
+			if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT) != 0)
 				panic("flushbufqueues: locked buf");
+			bremfreel(bp);
 			mtx_unlock(&bqlock);
-			bremfree(bp);
 			brelse(bp);
 			return (1);
 		}